I’m an introvert, so I need plenty of “alone” time. If I don’t get enough, I’m not myself. I feel worn out and cranky. I get short with people, because every little annoyance seems magnified. I want to sneak away and hide for a while.
Spending time alone—reading, writing, or just hanging around my apartment doing nothing—recharges me. It’s like what author Jonathan Rauch writes:
“For introverts, to be alone with our thoughts is as restorative as sleeping, as nourishing as eating.”
Rauch’s own formula is to spend two hours alone recharging for every hour he spends socializing.
Extroverts, on the other hand, actually feel energized when they’re on-the-go or hanging out with others. Many extroverts get restless and bored when they have to be alone for too long. But me? I could spend hours (or days) alone and feel great.
So why do introverts need more alone time than extroverts? The answer is found in the wiring of our brains.
It’s All in Your Head
Our need for alone time has to do with a chemical called dopamine. Both introverts and extroverts have dopamine in their brains, but they respond to it differently.
What is dopamine? It’s a neurotransmitter that helps control your brain’s pleasure and reward centers. It makes us notice opportunities to get external rewards (like money, social status, and sex) and take action to get them.
Imagine you and your extroverted friend are at a bar. You both see an attractive person across the room. Dopamine floods both of your brains as you think about flirting with this person. Your extroverted friend feels a thrilling rush of “happiness hits” from dopamine. But you feel nervous and somewhat overwhelmed. Sound familiar?
This is because extroverts have a more active dopamine reward network than introverts. Basically, they need more dopamine to feel its pleasant effects, explains Dr. Marti Olsen Laney in her book The Introvert Advantage: How Quiet People Can Thrive in an Extrovert World.
For introverts, too much of a good thing really is too much. We feel overstimulated when dopamine floods our brains.
When we spend time alone, we’re not faced with situations like talking to an attractive stranger. Essentially we’re lowering our level of external stimulation. Being alone feels just right for our dopamine-sensitive system.
Acetylcholine Is Where It’s At
Forget dopamine. Introverts would rather bask in another neurotransmitter called acetylcholine, explains Christine Fonseca in her book Quiet Kids: Help Your Introverted Child Succeed in an Extroverted World. Like dopamine, acetylcholine is also linked to pleasure. The difference is, acetylcholine makes us feel good when we turn inward. It powers our abilities to think deeply, reflect, and focus intensely on just one thing for a long period of time.
This helps further explain why introverts like being alone: it’s easier to turn inward when we’re not paying attention to other people.
Let Us Rest and Digest
According to Laney, everyone’s nervous system has two modes: parasympathetic and sympathetic. When we use the parasympathetic side (nicknamed the “rest and digest” side), we feel calm and are focused inwardly. Our body conserves energy and withdraws from the environment; muscles relax, energy is stored, food is metabolized, pupils constrict to reduce light, and our heart rate and blood pressure slow. The neurotransmitter acetylcholine increases blood flow and alertness in the front of the brain.
The sympathetic side is known as the “full-throttle” or “fight, fright, or flight” system. This side mobilizes us toward discovering new things and makes us active, daring, or inquisitive. The brain becomes alert and hyper-focused on its surroundings. Blood sugar and free fatty acids are elevated to give us more energy, and digestion is slowed. Thinking is reduced, and we become prepared to make snap decisions.
Of course, introverts and extroverts use both sides of their nervous system at different times. But just like introverts and extroverts respond differently to dopamine, we prefer different sides of the nervous system. You can probably guess which side introverts prefer: the parasympathetic side.
Are You Getting Enough Alone Time?
It can be hard to get enough alone time. We may feel guilty when we turn down social plans or tell our significant other we want a night to ourselves. However, not getting enough alone time can affect us physically and emotionally. According to Laney, you may not be getting enough alone time if you regularly experience some of these symptoms:
- Trouble sleeping or eating
- Frequent colds, headaches, back pains, or allergies
- Feeling anxious, agitated, irritable, and “snappish”
- Unable to think, concentrate, or make decisions
- Confused and discombobulated, as if you are dashing from thing to thing in a blur
- Trapped and wondering what is the meaning of life
- Drained, tired, and put-upon
- Disconnected from yourself
What should you do? Make it a priority to include alone time in your day, even if it’s only a few minutes of catching your breath alone in your car or bedroom. Laney writes, “Many introverts have felt so stigmatized about the private, reserved aspect of their nature that they have not allowed themselves the time to develop effective restorative practices. It’s time to change that!” 
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